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KVM: selftests: Add basic selftest for guest_memfd()
Add a selftest to verify the basic functionality of guest_memfd(): + file descriptor created with the guest_memfd() ioctl does not allow read/write/mmap operations + file size and block size as returned from fstat are as expected + fallocate on the fd checks that offset/length on fallocate(FALLOC_FL_PUNCH_HOLE) should be page aligned + invalid inputs (misaligned size, invalid flags) are rejected + file size and inode are unique (the innocuous-sounding anon_inode_getfile() backs all files with a single inode...) Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com> Co-developed-by: Ackerley Tng <ackerleytng@google.com> Signed-off-by: Ackerley Tng <ackerleytng@google.com> Co-developed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Co-developed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com>
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‎tools/testing/selftests/kvm/Makefile‎

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@@ -124,6 +124,7 @@ TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
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TEST_GEN_PROGS_x86_64 += demand_paging_test
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TEST_GEN_PROGS_x86_64 += dirty_log_test
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TEST_GEN_PROGS_x86_64 += dirty_log_perf_test
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TEST_GEN_PROGS_x86_64 += guest_memfd_test
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TEST_GEN_PROGS_x86_64 += guest_print_test
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TEST_GEN_PROGS_x86_64 += hardware_disable_test
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TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus

‎tools/testing/selftests/kvm/guest_memfd_test.c‎

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright Intel Corporation, 2023
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*
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* Author: Chao Peng <chao.p.peng@linux.intel.com>
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*/
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#define _GNU_SOURCE
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#include "test_util.h"
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#include "kvm_util_base.h"
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#include <linux/bitmap.h>
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#include <linux/falloc.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#include <stdio.h>
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#include <fcntl.h>
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static void test_file_read_write(int fd)
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{
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char buf[64];
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TEST_ASSERT(read(fd, buf, sizeof(buf)) < 0,
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"read on a guest_mem fd should fail");
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TEST_ASSERT(write(fd, buf, sizeof(buf)) < 0,
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"write on a guest_mem fd should fail");
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TEST_ASSERT(pread(fd, buf, sizeof(buf), 0) < 0,
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"pread on a guest_mem fd should fail");
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TEST_ASSERT(pwrite(fd, buf, sizeof(buf), 0) < 0,
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"pwrite on a guest_mem fd should fail");
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}
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static void test_mmap(int fd, size_t page_size)
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{
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char *mem;
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mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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TEST_ASSERT_EQ(mem, MAP_FAILED);
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}
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static void test_file_size(int fd, size_t page_size, size_t total_size)
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{
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struct stat sb;
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int ret;
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ret = fstat(fd, &sb);
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TEST_ASSERT(!ret, "fstat should succeed");
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TEST_ASSERT_EQ(sb.st_size, total_size);
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TEST_ASSERT_EQ(sb.st_blksize, page_size);
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}
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static void test_fallocate(int fd, size_t page_size, size_t total_size)
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{
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int ret;
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, total_size);
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TEST_ASSERT(!ret, "fallocate with aligned offset and size should succeed");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
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page_size - 1, page_size);
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TEST_ASSERT(ret, "fallocate with unaligned offset should fail");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size, page_size);
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TEST_ASSERT(ret, "fallocate beginning at total_size should fail");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, total_size + page_size, page_size);
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TEST_ASSERT(ret, "fallocate beginning after total_size should fail");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
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total_size, page_size);
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TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) at total_size should succeed");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
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total_size + page_size, page_size);
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TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) after total_size should succeed");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
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page_size, page_size - 1);
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TEST_ASSERT(ret, "fallocate with unaligned size should fail");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
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page_size, page_size);
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TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) with aligned offset and size should succeed");
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, page_size, page_size);
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TEST_ASSERT(!ret, "fallocate to restore punched hole should succeed");
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}
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static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size)
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{
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struct {
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off_t offset;
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off_t len;
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} testcases[] = {
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{0, 1},
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{0, page_size - 1},
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{0, page_size + 1},
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{1, 1},
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{1, page_size - 1},
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{1, page_size},
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{1, page_size + 1},
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{page_size, 1},
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{page_size, page_size - 1},
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{page_size, page_size + 1},
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};
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int ret, i;
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for (i = 0; i < ARRAY_SIZE(testcases); i++) {
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ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
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testcases[i].offset, testcases[i].len);
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TEST_ASSERT(ret == -1 && errno == EINVAL,
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"PUNCH_HOLE with !PAGE_SIZE offset (%lx) and/or length (%lx) should fail",
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testcases[i].offset, testcases[i].len);
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}
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}
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static void test_create_guest_memfd_invalid(struct kvm_vm *vm)
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{
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uint64_t valid_flags = 0;
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size_t page_size = getpagesize();
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uint64_t flag;
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size_t size;
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int fd;
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for (size = 1; size < page_size; size++) {
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fd = __vm_create_guest_memfd(vm, size, 0);
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TEST_ASSERT(fd == -1 && errno == EINVAL,
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"guest_memfd() with non-page-aligned page size '0x%lx' should fail with EINVAL",
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size);
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}
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if (thp_configured()) {
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for (size = page_size * 2; size < get_trans_hugepagesz(); size += page_size) {
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fd = __vm_create_guest_memfd(vm, size, KVM_GUEST_MEMFD_ALLOW_HUGEPAGE);
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TEST_ASSERT(fd == -1 && errno == EINVAL,
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"guest_memfd() with non-hugepage-aligned page size '0x%lx' should fail with EINVAL",
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size);
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}
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valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE;
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}
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for (flag = 1; flag; flag <<= 1) {
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uint64_t bit;
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if (flag & valid_flags)
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continue;
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fd = __vm_create_guest_memfd(vm, page_size, flag);
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TEST_ASSERT(fd == -1 && errno == EINVAL,
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"guest_memfd() with flag '0x%lx' should fail with EINVAL",
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flag);
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for_each_set_bit(bit, &valid_flags, 64) {
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fd = __vm_create_guest_memfd(vm, page_size, flag | BIT_ULL(bit));
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TEST_ASSERT(fd == -1 && errno == EINVAL,
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"guest_memfd() with flags '0x%llx' should fail with EINVAL",
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flag | BIT_ULL(bit));
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}
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}
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}
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static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
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{
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int fd1, fd2, ret;
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struct stat st1, st2;
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fd1 = __vm_create_guest_memfd(vm, 4096, 0);
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TEST_ASSERT(fd1 != -1, "memfd creation should succeed");
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ret = fstat(fd1, &st1);
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TEST_ASSERT(ret != -1, "memfd fstat should succeed");
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TEST_ASSERT(st1.st_size == 4096, "memfd st_size should match requested size");
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fd2 = __vm_create_guest_memfd(vm, 8192, 0);
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TEST_ASSERT(fd2 != -1, "memfd creation should succeed");
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ret = fstat(fd2, &st2);
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TEST_ASSERT(ret != -1, "memfd fstat should succeed");
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TEST_ASSERT(st2.st_size == 8192, "second memfd st_size should match requested size");
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ret = fstat(fd1, &st1);
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TEST_ASSERT(ret != -1, "memfd fstat should succeed");
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TEST_ASSERT(st1.st_size == 4096, "first memfd st_size should still match requested size");
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TEST_ASSERT(st1.st_ino != st2.st_ino, "different memfd should have different inode numbers");
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}
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int main(int argc, char *argv[])
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{
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size_t page_size;
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size_t total_size;
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int fd;
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struct kvm_vm *vm;
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TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
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page_size = getpagesize();
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total_size = page_size * 4;
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vm = vm_create_barebones();
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test_create_guest_memfd_invalid(vm);
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test_create_guest_memfd_multiple(vm);
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fd = vm_create_guest_memfd(vm, total_size, 0);
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test_file_read_write(fd);
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test_mmap(fd, page_size);
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test_file_size(fd, page_size, total_size);
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test_fallocate(fd, page_size, total_size);
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test_invalid_punch_hole(fd, page_size, total_size);
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close(fd);
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}

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